Chrome tanning material and process of making same



Jam 8, 1929.

C. D. MARLATT ET AL CHROME TANNING MATERIAL AND PROCESS OF MAKING SAME Filed April 15, 1926 A QM ATTORNEY Patented Jan. 8, 1929.

UNITED STATES PATIENT OFFICE.

CLYDE D. MARLATT, OF NEWARK, AND WALTER H. DICKERSON, DECEASED, OF EAST ORANGE, NEW JERSEY, BY CONSTANCE H. DICKE RSON, EXECUTRIX, OF NEW YORK, N. Y. SAID MARLATT ASSIGNOR'TO INDUSTRIAL WASTE PRODUCTS COR-' PORATION, OF NEW YORK, N. Y., A. CORPORATION OF DELAWARE.

CHROME TANNING MATERIAL AND PROCESS OF MAKING SAME.

Application filed April 15, 1926. Serial No. 102,292.

The present invention has to do with the converting of viscous syrupy liquids into the form of a dry product consisting of independent particles, and it relates particularly to the production of an improved one-bath chrome tannage product in dry form.

Chrome tannage is used largely in the tanning industry for the tanning of hides, skins and animal tissues. It is employed chiefly in the production of mechanical leathers such as belting and the like forthe reason that it produces a leather which is firmer, harder wearing and more resistant to heat than bark tanned leathers. Chrome tannage consists principally of basic chromium sulfate, the active tanning constituent being chromium oxide derived from the sulfate and made available during the tanning process. It may or may not contain certain other constituents having tanning properties, such as for instance aluminum sulfate.

- As ordinarily manufactured one -bath chrome tannage is produced by preparing a solution of bi-chromate of soda and adding, an appropriate reducing agent, such as sug-' ar, glucose, sodium bi-sulfite, sulfur dioxide, or the like. to effect the desired chemical reaction. The resulting product is essentially a solution of basic chromium sulfate together with whatever other matter is formed incidentally during the reaction. This liquor obtained in the commercial manufacture of the product is designated in this application as chrome tannage liquor. This basic chromium sulfate solution may be distributed directly to the tanning trade, in which case it is diluted by the tanner as desired and used. However,due largely to the problem of trans portation, the chrome tannage liquor as manufact-ured is commonly dried to solid form and then disintegrated to reasonably fine size and supplied to the trade in this condition, in which case it is redissolved in water b the tanner and the resulting solution emp oyed of practical commercial operation, and it has been found that it is not feasible to conduct the manufacture in such fashion that the solid content of the liquor say Due to the gummy, syrupy character of the liquor the conversion of it into the form of a dry product which can be satisfactorily stored and handled presents particular difficulty. The present invention provides a proc ess by which such conversion can be accomplished and by which itcan be accomplished in a continuous, economical and convenient process of manufacture. The invention is applicable not only to the conversion of chrome substantially exceeds tannage liquor into appropriate dry form but also to the treatment of other liquids having the same general physical characteristics as chrome tannage such as, for instance, waste sulfite liquor, glue, sugar syrups, molasses,

malt extracts and, in general, any liquids which at some degree of concentration are viscous, sticky and syrupy in character. The individual particles .of the ultimate dry conversion product of any of this class of materials are small spherical bodies of glazed or glass like appearanceas will be more fully described in the following portions of the commercial manufacture of the product systematic tests of this nature are essential to the continued production of a high quality product. tannage should exhibit the required excellencein tanning properties and'also the dry product should be as nearly completely solu-' ble in water as possible. Heretofore the chrome tannage products exhibiting the best tanning properties have, when produced in 'dry form, fallen appreciably short of complete solubility. It is an object of this invention to provide a one-bath chrome tannage in dryform having tanning properties equal to those of the best chrome tannage products heretofore produced and which at the same A satisfactory one-bath chromev syrupy liquids into an improved dry physical form involves broadly breaking up the syrup into separate small particles and introducing these particles into contact with a gaseous drying medium. For the purpose of more clearly describing the process and the features of regulation and control which are essential. to the production of the improved product of this invention, the apparatus by means of which the process is carried out has been illustrated in the arrangement drawing annexed hereto and made a part of this specification.

In the drawing, 1 indicates the spray-drying tower or chamber, here shown as a vertical cylindrical tower built up in sections to the requisite height. The liquor to be evaporated issprayed into the upper port on of the tower 1 through the medium of nozzles 2. The chrome tannage liquor as manufactured is delivered initially to storage tank 3 from where it is continuously withdrawn through discharge line 4 by means of the pump 5 which also serves as the delivery pump for supplying liquor to the spray nozzles 2 at the desired pressure. Between the discharge side of the pump 5 and the spray nozzles is a group of steam heated coils 6 through which the liquor issuing from the pump is forced in order that it may be preheated to the proper temperature for delivery to the nozzles. The preheated liquid is conveyed from the heater 6 through line 7 to the top of the drying tower, where it is discharged into. a manifold pipe 8 communieating with the individual feed pipes 9 which supply the respective nozzles.

The hot dryin air is delivered tothe upper portion of the rying tower 1 by means of pipe 10. As here shown the air is heated in an oil fired furnace 11, the cold fresh air being inducted into the furnace through a delivery line 12 communicating with the out side air, passed through the furnace as combustion air for the oil burner and then delivered to the line 10 leading to the drying tower. The drying medium thus consists of the products of combustion taken directly from the furnace and utilized in the drying chamber. The gas thus enters the drying tower at its upper portion and the subdivided liquor or syrup contacts with the gas during the early portion of its flow through the tower. The gas, together with the subdivided liquor suspended in it, passes downperature conditions of the process. The temperature at 13 is that of the drying air as it is supplied to the tower 1. The temperature indicated at 14 is that of the mixed drying gas and material being dried at, that point along the height of the tower at which desiccation is substantially completed. This temperature is in effect the drying ten'ipcrature in the sense that it is the maximum temperature to which the dried particles are exposed. Slots or openings 16 are provided around the circun'lterence of the tower near its lower end so that, if desired, cooling air at ordinary room tcn'iperature may be admitted to the.

tower. The temperature indicated at 15 is the temperature of the dried product after the cooling and drying have been completed. The dried product is separated from the moisture laden drying gas. in a centrifugal collector 17, the product issuing continuously at the bottom of the collector as indicated at 18. The gases and vapors pass out of the col.- lector through line 19 to the air washer 20 wherein any of the dried product still carried by the gas is washed out. A pump 21 operated by an electric motor 22 is placed at the discharge side of the air washer and serves -to establish the pressure differential which maintains the flow through the entire apparatus. The purified gas issuing from the air washer is discharged to atmosphere through stack 23.

Preheating of the liquor before admission to the drying tower has been found to rendei the liquor easier to handle, to produce a l etter drying action and to give better economy of operation. In fact, it appears that it is necessary to the success of the process that the liquor be preheated. and the extent to which the preheating is carried out is somewhat critical. Experience hasshown that a liquor temperature of about 238 degrees F. is satisfactory. With a liquor temperature which is too high an appreciable amount of insoluble material is obtained in the finished product. This appears to be due to the presence of undersized particles produced under those conditions and which are over-dried to a greater or lesser extent. If an excessive 1y low temperature of preheating is employed, under-drying of the material with consequent gumming and sticking to the parts of the apparatus results. The pressure in the spray-drying toweris substantially atmospheric, or slightly above, and the permisslble liquor temperature of 238 degrees about corresponds to the boiling point of the liquor at the pressure to which the atomized lul lIJ

' takes place. The accuracy of this explanation is not, however, insisted upon, the fact being that when a liquor temperature appre-,

ciably in excess of 238 degrees is employed the product exhibits a relatively high proportion of insolubles. The desired moisture content of the finished product is about 6% which corresponds to the normal water of constitution content. The present process permits of the minute regulation of conditions required to produce the product in this condition.

A particular characteristic of the improved chrome tannage of this invention is the extent to which it is soluble in water and the excellence of the tanning properties which it exhibits. In the ordinary manufacture of dry one-bath chrome tannage where the drying operation is conducted in tray evaporators, vacuum pans, drums or the like, it has heretofore been impossible to produce commercially a chrome tannage product of substantially complete solubility which at the same time possesses the best tanning properties. This is probably due to lack of complete uniformity in drying, as is evidenced by the presenceof light green over-dried portions in the product. Experience has shown that when a product exhibiting the desired tanning properties was obtained the commercial run of the product, after being vacuum dried and disintegrated to the proper size, was from 99.5% to 99.8%. With this product a residue of insoluble, solid material remained in the bottom ofthe tanks and vats in which the chrome tannage was dissolved. The practical effect of this was that the tanner, in stirring the solution with his paddle, could always feel the insoluble residue in the bottom of the tank and was therefore impressed with the fact that the product was not wholly soluble. When this identical product is spray-dried according to the process of this invention the commercial run of the dried product is practically completely soluble, the range of solubility being from about 99.75% to 99.99%. When this product is dissolved in the tanks no residue can be detected in the bottom. The solubility is so nearly complete that the minute amount of insoluble matter present remains easily in suspension, and for all practical purposes the product is completely soluble. In fact, in the commercial run of the product it is often very difiicult to detect the presence of insoluble matter except by carefully filtering the dissolved product and examining the filter paper for the green residue which indicates the presence of undissolved matter.

Chrome tannage has been dealt with specifi-' cally in this application partly for the reason that it presents greater difficulties in processing than do the other materials of the same.

general class above defined. 'As far as we have been able to determine,- all sticky, viscous, syrupy materials may, by means of the present process, be converted into dry product having certain well-defined characteristics in common. For instance, with any of this class of materials the dry conversion product is composed of independent nonadhering particles of spherical conformation. This renders the product easy to handle particularly in the respect that it is free flowing, for the reason that the particles roll easil upon each other and the dry product thus ows or gours in the same fashion as does a liquid.

ometimes the particles are hollow and sometimes they are solid, and all intermediate types of particles ranging from thin walled bubble like particles to solid spheres may be found. When an appreciable proportion of solid particles occur a large surface proportionate to the total mass of the product is exposed. This gives rise to certain well defined advantages notable among which is the speed with which the product goes into solution. Inthe ordinary commercial run of dry chrome tannage, for instance, the product goes into solution in a materially shorter time than any chrome tannage product heretofore roduced by the ordinary methods of manu acture. The particles of the product roduced from materials of the above de ed class are smooth, shiny and glassy in appearance. Each particle resembles in physical appearance a small drop or bubble of an amorphous substa'nce such as glass. Each particle is apparently unitary and homogeneous in structure. The hollow particles when subjected to a substantial amount ofpressurebreak up into irregular fragments resembling in appearance the broken portions of a dry egg shell. The particles are not in any sense composite or granular and are not composed of independent component parts which have been aggregated to form the ultimate particle. Each particle appears to be a continuous amorphous mass. This characteristic type of particle resulting from the process herein disclosed has many advantages in the arts, notably that of enabling liquids normally sticky and syrupy in charactor to be produced as a dry product which is easy to handle, which is to a surprising extent non-hygroscopic, which will retain its physical characteristics under the ordinary conditions of packaging, shipment and storage, and the'like.

A particularly important feature of the present process is that it provides for the conversion of the class of materials indicated into the physical form just described by means of a continuous process of manufac ture. Other processes have heretofore been employed for producing materials of this general class in the form of dr products of varying physical characteristics. Aside from the characteristics of quality which are found in the present product as compared with those of products of this general class heretofore produced, the present process r the like, heretofore employed with materials of, this class. With chrome tannage, for instance, the principal standard commercial method of manufacture heretofore employed involved drying the chrome tannage liquor in shelf vacuum pan dryers. With this system for each batch of material it was necessary to fill each of the evaporator trays independently with liquor, introduce the filled trays into the apparatus, evacuate and heat the apparatus and maintain these conditions un til the product wasdry. The drying period was a matter of several hours in contrast with the drying period of a few seconds in the present process. After drying was complete it was necessary to break the vacuum, withdraw the trays withthe dried material in them scrape or chop the dried cake out of the pans and then run the product through a disintegrating mill to reduce it to appropriate size. The savings in labor, time and utilization of heat afior'ded by the present process have proven to be so pronounced as to effectually render the tray drying process just described obsolete on the basis of competitive commercial use. Additionally, in the present process all of the conditions of operation are subject to minute and convenient control at all times. Continuous operation is effected by reason of thefact that the raw syrup 'or liquor is supplied to the storage tank' 3 from time to time from whence it is continuously withdrawn and supplied to the tower. The finished product continuously issues from the bottom of the tower and the time of but one laborer is required to place barrels or other suitable receptacles under the discharge "outlet and closethe packages as they are filled. This phase of the present process is important from thestandpoint of commercial operation and, considered from this viewpoint, the invention lies essentially in the fact that the process takes the raw liquor, or syrup continuously, putsitthrough all of the necessary preliminary treatment such as preheating, or in the case of sugar syrups, clarifying, filtering and the like,

passes the preliminarily treated liquor to the drying tower and continuously produces and co lects the dried product.

The invention contemplates a process for continuously converting materials of the class described into a dry product of the class described. Tt contemplates specifically the features of the process which are essential to the production of a. product of the class described. It also contemplates the product in so far as the product difi'ers from products of this general class heretofore produced. The invention specifically contemplates the improved chrome tannage product described herein which is practically completely soluble in water, is possessed of the desired excellence in tanning properties and is quickly soluble. which this improved chrome tannage product is produced.

The chrome tannage product of the present invention, therefore, when produced accord ing to the process of this invention is practically completely soluble in water and at the same time is of the desired excellence in tanning properties. Its tanning properties are equal to those of chrome tannage which heretofore couldbe produced only at a consider able sacrifice in total solubility. In addition, the present product is quickly soluble.

What is claimed is:

. 1. The process of converting chrome tannage liquor into dry powder form which comprises spraying said liquor into a hot gaseous drying medium and heating said liquor prior to. the spraying thereof to substantially 238 F.

2. The process of producing a dry chrome tannage product which comprises preparing a chrome tannage liquor having about 60% of solids, heating said liquor to substanlt also contemplates the process bytially 238 degrees F. and then spraying said heated liquor into a hot gaseous drying medium at approximately atmospheric pressure. 3. The process of producing a dry chrome tannage product which comprises forming a solution of a bichromate, adding an appropriate reducing agent thereto to form the chrome tannage liquor, preheating the said liquid to substantially 238 degrees F. and spray-drying said preheated liquor in a heated gaseous medium at approximately atmospheric pressure.

4. A chrome tannage product in dry form free from under-dried gummy portions and free from light green over-dried portions.

5. Chrome tannage in the form of a dry product composed of independent spherical glazed particles, dry in appearance, dark green in color, free from light green overdried portions, and having a Water content substantially corresponding to the normal water of constitution content of the product. 6. A spray-dried chrome tannage product which is dry to the touch, is free flowing and not sticky and consists of small spherical particles of a uniform dark green color.

7. A dry chrome tannage product of the class described having tanning properties particles having tanning properties equal to those of the best chrome tannage products heretofore produced and exhibitin in the commercial run of the product a solu ility of from 99.7 5% to 99.99%.

9. A chrome tannage product in dry form,

the average commercial run of which has tanning properties equal to those of the best commercial chrome tannage products heretofore available and when stirred into a vat of water according to the usual tanning process is absorbed by the water Without perceptible residue.

10. A, chrome tannage product in the form of small spherical glassy particles, uniformly dark green in color, dry in appearance and having a water content of about 6%.

In testimony whereof we aflix our signatures.

CLYDE D. MARLATT. CONSTANCE H. DICKERSON, Emeeutfiw of the Last Will and Testament of Walter H Dickerson, Deceased. 

